INTEGRAL discovered a new hard X-ray transient, IGR J18179-1621, during
the inner Galactic disk observations performed on 2012-02-29 from 02:20
to 15:41 UTC.

The source was detected in the IBIS/ISGRI mosaic at a
significance level of 16 σ (effective exposure time 30 ks)
in the 20-40 keV energy band. The corresponding flux was
16±1 mCrab (1.2±0.1 × 10-10 erg/s/cm2) (uncertainties are 68% c.l.).

The source was also detected by JEM-X at a significance level of 8
σ in the 3-10 keV energy band and 10 σ in the 10-25 keV energy
band. The corresponding fluxes were 17.7±2.2 mCrab (3.0±0.4 × 10-10
erg/s/cm2) and 36.4±3.6 mCrab (4.4±0.4 × 10-10 erg/s/cm2), respectively (effective exposure time 11.9 ks).
The best source position determined with the two JEM-X instruments is
RA=274.467 (18h17m52s);
DEC=-16.357 (-16d21'25")
(J2000) with an associated uncertainty of 1.5 arcmin.

The combined JEM-X and IBIS/ISGRI spectrum can be well described (χ2red/d.o.f.=0.4/12) by a cut-off power-law (Γ=-0.5
± 0.5, Ecutoff=4.9-0.9+1.5 keV) plus a broad Gaussian absorption line
(Ecentroid=20.8-1.8+1.4 keV, σ=3.0-1.3+1.8 keV, τ=10-4+5, model
uncertainties at 90% c.l.).
The 3-50 keV flux estimated from the spectral fit is 1.0 × 10-9 erg/s/cm2.
If the absorption line is interpreted as due to cyclotron scattering,
this new source would be a high mass X-ray binary pulsar with a magnetic
field in the emitting region of ~1.7 × 1012 Gauss. However, the non-detection of a higher harmonic might indicate that a model with two emission components could also be used (see also the case of X-Per, Doroshenko et al., 2012, arXiv:1202.6271).

Multiwavelength follow-up observations are encouraged to unveil the
nature of this transient.